Consider this no parking sign. Instead of stating the fine, the signmaker states the range of the fine. At this point, it's up to the observer to have a conversation with himself. "Well, maybe I'll just get a $50 fine. Hmmm, why would that happen? With my luck, it'll be the maximum… I'll just park somewhere else."
It's not an announcement, it's an invitation to a little internal drama.
Too often, we don't give people a chance to fill in the blanks.